Induction heating coil



H. A. STRICKLAND, JR

INDUCTION HEATING COIL July 4, 1950 Filed Dec. 27, 1946 HM WWW FIG. 5Q

INVENTOR Harokl Q. Strickland Jr,

BYMQ.M

ATTORNEY Patented July '4, 1950 2,513,376 INDUCTION HEATING 0011.

Harold A. Strickland, J r., Detroit, Mich, assignor, by mesne assignments, to The Ohio Crankshaft Company, Cleveland, Ohio, a corporation of Ohio Application December 27, 1945, Serial No. 718,648

3 Claims. (01. 219-47) This invention relates to induction heating coils. The primary application of the coil is in connection with the heating of fiat metal surfaces.

Among the objects of the invention are to provide an induction heating coil in loop form having means for extending the normal heatingarea of the coil to the intermediate region formed by the loop; to provide means for extending magnetic flux of a conductor laterally from the con- 1 ductor to enlarge the area of power distribution thereof; to provide means for increasing the efiiciency of the heating coil by reducing heat losses in the flux-directing elements of the loop; and to provide novel means for securing through a loop conductor a plurality of magnetic flux-conducting plates in such manner as to cover the region formed between the turn sections of the conductor.

The following description is directed to a form of the invention which may be preferred, the details of the structure being shown in the accompanying drawing, in which:

Figure l is a plan view of the induction heating coil;

Figure 2 is an elevation in section of the coil along lines 2-2 of Figure l; and

Figure 3 is a further section at right angles to the plane of Figure 2, taken along line 3-3 of Figure 2.

Induction heating coils take many forms depending upon the particular uses to which the coils may be put. In Figure l of the drawing I have shown the coil in the form of a loop having extended length in relation to width so as to permit fairly wide coverage of a fiat workpiece, such as a metal plate, placed directly beneath the coil. The structure includes a tubular copper conductor I having side sections 2 and 3 and end sections 4 and 5, the coil terminals being indicated at 6 and l, at which connections to a combined source of electrical current and coolant are made. The side sections 2 and 3 are parallel, and together with the end sections enclose an area 8 which normally would not receive a substantial amount of magnetic flux from the conductor, and hence the heating action of the coil at this interior region would be low, if not negligible.

In order to overcome the deficiency of the coil in failing to heat the entire area enclosed thereby, use is made of a plurality of laminations which extend over this intermediate coil area in the form of a grid. As shown in Figure 1, a preferable method of securing the laminations is to secure separate lamination plates 9 of iron or modified steel to the inner edge of one of the long coil sections 2 or 3, the connection being made to section 2 as shown in Figure 1 of the drawing. These plates are flat with the flat surfaces thereof transverse to the coil plane and of a width approximately that of the diameter of the conductor itself, and one end of each plate is brazed or otherwise attached to the inner side if! of the conductor with a uniform spacing between successive plates. The length of each plate extends almost across the area 8, the unattached ends of the plates terminating short of the opposite conductor section 3 sufficiently to permit placement between the conductor 3 and these free ends of plates 9 of an insulation plate M. This insulation plate may be of mica or similar non-magnetic, dielectric, and heat-resistant material and is secured to the coil section 3 by any appropriate means, such as cementing, as indicated in the showing of Figure 3.

Additional lamination plates l2 and is are also secured to the end sections 4 and 5 of the coil, the point of securement being similarly the inner side of the coil, and the plates extending inwarolly to points adjacent the outermost or end plates 9 of the lateral laminations. These plates also are fiat with their planes of placement being transverse to the plane of the coil. By this construction two inwardly projecting end lamination units are provided which with the lateral unit overlie approximately the entire interior area 8 of the coil.

The utility of the extended laminations fixed within the inner area of the coil lies in the fact that through their use magnetic flux generated by the current flowing in the conductor is afforded a path of reduced reluctance which permits and enforces a path of flux movement extending along the entire length of the laminations and through the workpiece directly beneath them. This greatly improves the power factor of the coil. Also, instead of having the flux localized completely about the conductors, it is spread inwardly to include the workpiece area underlying the laminations, and thus the heating action of the fiux is distributed further toward the inner area of the loop, as well as applied to the area directly adjacent the conductors.

In use the loop such as described is placed to overlie a flat metal plate or other workpiece, and the area beneath the workpiece is heated. Usually the apparatus lends itself to the application of heat to a moving strip or band of metal so.

that a progressive heat treatment becomes readily possible through use of this unit. Because of the spread of heat application brought about by use of the internal laminations as described, the time period for heat application on a moving strip beneath the unit is decreased.

As mentioned, the showing is illustrative. Obviously modification of the precise form of the invention may be made, as, for example, in the configuration of the loop, which may be circular, rectangular, linear in the form of a single conductor, or otherwise shaped. Also, the exact form of the laminations may be varied to suit conditions. Accordingly, no restriction is intended to the form of the invention as described other than may be required by the claims as hereto appended.

What is claimed is:

1. An induction heating coil comprising a single turn, of electrical conductor enclosing an open area, and spaced magnetically permeable laminations extending from a section of th inner side of said conductor over said enclosed area, said laminations being insulated from each other except at the point of attachment to the conductor.

2. An induction heating coil comprising a single turn of electrical conductor lying in a fiat plane having side and end sections, magneticallypermeable laminations comprising flat plates attached to one of said side sections and to both of said end sections with the plane of the laminated plates extending at right angles to the plane of the loop, at least said plates attached to said one of said side sections extending a substantial distance across the space between said sections, whereby the area formed by the loop is approximately filled by said laminations.

3. An induction heating coil comprising a single turn of electrical conductor enclosing an open area, and spaced magnetically permeable laminations extending from a section of the inner side of said conductor substantially over said enclosed area in its entirety.

4. Apparatus of the class described comprising an electrical conductor adapted to have current fiowed therethrough to establish a flux field, and spaced magnetically permeable plates extending a substantial distance laterally from said conductor and on one side only of a plane passing through a surface of said conductor, whereby the effective area of magnetic flux distribution is enlarged in the direction of the plates.

5. An induction heating unit comprising a sec- 4 tion of electrical conductor adapted to have electric currents flowed therethrough to establish a flux field therearound, and magnetically permeable plates attached to said conductor on at least one face thereof and extending laterally therefrom on one side only of a plane passing through a surface of said conductor to form a grid area adapted to overlie a workpiece to be heated, said plates being insulatingly spaced from each other except at the point of conductor attachment.

6. An induction heating coil comprising a single turn of tubular electrical conductor adapted to receive a coolant, spaced magnetically permeable plates attached to the conductor and extending laterally therefrom to form a combined conductor and plate grid adapted to overlie a workpiece for inductive heating, said plates being spaced from each other except at th point of attachment to the conductor.

7. An induction heating unit comprising a tubular copper electrical conductor, and ironcontaining plates attached to the conductor at a series of uniformly spaced point and extending laterally a substantial distance from the conductor on one side only of a plane passing through the surface of said conductor, whereby the efiective area of heat application of the unit is enlarged.

8. An induction heating coil formed of at least one turn of electrical conductor enclosing an open area, and spaced magnetically permeable laminations extending from a section of the inner side of said conductor over said enclosed area, said laminations being insulated from each other except atthe point of attachment to the conductor.

HAROLD A. STRICKLAND, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,981,629 Northrup Nov. 20, 1934 1,981,632 Northrup Nov. 20, 1934 2,053,176 Bouwers Sept. 1, 1936 2,182,820 Pisarev Dec. 12,1939 2,212,522 Hart et al. Aug. 27, 1940 2,228,136 Hart Jan. 7, 1941 2,329,944 Schakenback Sept. 21, 1943 2,424,816 Groven et al. July 29, 1947 2,459,971 Stanton Jan. 25, 1949 

